Fluorocarbons have numerous biomedical applications because of their essential characteristics of high chemical and biological inertness and their capacity to dissolve a considerable amount of gases, particularly oxygen, carbon dioxide and air per unit volume. Indeed, at 37.degree. C. under a pure oxygen atmosphere, a fluorocarbon can dissolve about a 50% volume of oxygen.
Compositions of fluorocarbons can also be used for the treatment of wounds, for example burns, as described in U.S. Pat. No. 4,366,169. According to this disclosure, the wound is put in contact with a liquid fluorocarbon directly, or indirectly through a dressing, for example a sponge, gauze, foam, dispersion or gel into which the fluorocarbon has been incorporated. However, the '169 patent does not disclose a high concentration fluorocarbon formulation or a procedure for preparing a fluorocarbon-rich gel.
High concentration fluorocarbon formulations can increase the gas-transfer capacity of preparations for topical application, improving their therapeutic effects and protecting the tissues coated therewith. Highly viscous preparations of this type can be easily applied to the wounded tissues.
Fluorocarbons have been used in the form of emulsions or water-rich gels. Known gel formulations contain low concentrations of fluorocarbons and require stabilizing or thickening agents to maintain a desirable consistency. Thus, U.S. Pat. No. 5,073,378 describes compositions for the treatment of burns, obtained from solutions of collagen, containing a growth-factor derived from platelets, and a fluorocarbon phase whose perfluorocarbon content is low. U.S. Pat. No. 4,917,930 and EP-A-0158996 describe compositions in the form of fluorocarbon emulsions comprising no more than 50% fluorocarbon by weight, or about 25% fluorocarbon by volume. These compositions are obtained by preparing an initial dispersion comprising a fluorocarbon and a surfactant complexed with the fluorocarbon, and then concentrating the fluorocarbon phase of the dispersion, for example by centrifugation, separating the fluorocarbon-rich phase, and redispersing this phase in an aqueous medium optionally containing a surfactant. Although this procedure makes it possible to limit the quantity of surfactant used, does not provide formulations having fluorocarbon concentrations greater than 50% by weight. The emulsions obtained by this process are used for injectable purposes.
U.S. Pat. No. 4,569,784 describes a stable gel of fluorocarbon also comprising no more than 50% by volume of fluorocarbon, which requires considerable quantities of surfactant for stabilization. This gel is prepared by a similar complex procedure of concentrating an emulsion by centrifugation, and requires high-pressure apparatus or the use of ultrasounds.
The document FR-A-2 630 347 describes fluorocarbon gels comprising, by contrast with those described in the above patents, a high proportion of water, about 60 to 98% by weight.
WO-A-93/09762 describes the use of fluorocarbon suspensions or emulsions for intravascular applications, containing at most 90 g/100 ml (about 50% v/v).
WO-A-90/15807 describes the use of phosphorous fluorinated surfactants in fluorocarbon emulsions and other compositions containing at most 70% in volume of fluorocarbons.
Obraztsov (poster contribution to the Vth ISBS, San Diego Calif., U.S.A., March 1993) describes an emulsion prepared from a mixture of fluorocarbons containing perfluorodecalin (80% w/v, 40% v/v), emulsified using a polyoxyethylene/polyoxypropylene copolymer (Proxanol 268) and gelified by 1,2-propyleneglycol. Preliminary studies have shown that this emulsion has a beneficial effect on the speed of cicatrization of burns and surgical wounds (activation of keratinocytes) and should be more efficacious than the biostimulating medicaments traditionally used (methyluracyl and solkoseryl). But the fluorocarbon content of these preparations does not exceed 50% by volume and the gelification is obtained by the use of a non-surfactant diol.